1. Field of the Invention
The present invention relates to a photo mask having an assist pattern formed adjacent to a pattern, a method of manufacturing a semiconductor device using the photo mask, and a method of generating data for the photo mask.
2. Description of the Related Art
In the prior art, in forming fine hole patterns using a photo mask, resolution is improved by locating assist patterns with the same shape as that of main patterns, around the main patterns (FIG. 1 in Jpn. Pat. Appln. KOKAI Publication No. 10-239827). However, it will be assumed that a photo mask is projected and exposed which has, as a part of the whole pattern, a pattern row of fine contiguous hole patterns 401 such as those shown in FIG. 33. FIG. 34 shows the addition of assist patterns 402 to the pattern row shown in FIG. 33. However, the mask pattern shown in FIG. 34 has an insufficient resolution for the hole patterns 401 and thus only a small lithography margin.
There is a technique to form an assist pattern adjacent to a pattern having periodicity with respect to its adjacent patterns (Jpn. Pat. Appln. KOKAI Publication No. 7-140639). It will be assumed that the assist pattern is formed adjacent to a pattern not having periodicity with respect to the adjacent patterns. That is, the assist pattern is located adjacent to a rectangular pattern in its latitudinal direction. Also in this case, the rectangular pattern has an insufficient resolution and thus only a small lithography margin.